By far the largest epidemic is going on inside hospitals and other health care facilities. The staph bug causing these infections resists treatment with a broad range of antibiotics. Because it attacks so many people with weakened immune systems, hospital-acquired MRSA accounts for the vast majority of fatal MRSA infections.

But another, unrelated strain of MRSA is circulating in communities across the U.S. This strain is resistant to first-line antibiotics.

News that MRSA is now killing at least 19,000 Americans each year has focused public attention on community-acquired MRSA. Where does it lurk? WebMD asked epidemiologist Jeff Hageman, one of the scientists tracking MRSA at the CDC.

"We see outbreaks in settings where there is crowding, a lot of skin contact, and, often, a lack of good hygiene," Hageman tells WebMD.

Hot spots for these outbreaks have been:

Athletic settings

Military barracks

Prisons

Schools

Interestingly, Hageman says day care centers have not been hot spots for MSRA outbreaks.

"It is kind of surprising to us that we have not received many reports of MRSA in day care," he says. "We hear lots of reports of MRSA in children, but not associated with day care. One reason is that day care centers already have policies in place to handle a wide variety of diseases. Those same policies would prevent MRSA infections."

Hageman says outbreaks happen when a person with an MRSA infection comes into direct skin-to-skin contact with another person -- or after a person uses a towel or other object that's been contaminated by an infected person.

But you can't avoid MRSA by avoiding so-called hot spots.

"Staph is found anywhere. One in three people carry staph on their skin. They can spread infections anywhere in the community," Hageman says.